A check valve can be located in the intake passage leading to a cylinder of an engine to obstruct fluid back-flow out of the cylinder into the intake passage. One application of such a check valve is in conjunction with a valve control system which causes the intake valve for the cylinder to open during the exhausting of exhaust gas from the cylinder (i.e., during an exhaust portion of the engine cycle). This can result in exhaust gas flowing from the cylinder back into the intake passage and reentering the cylinder with the subsequent incoming charge of air. The check valve obstructs fluid back-flow further into the intake passage.
A port can be located on the intake passage between the intake valve and check valve, and a chamber having a fixed opening connected to the bypass port to allow communication between the chamber and intake passage. The effective volume of the intake passage between the check valve and intake valve is thereby increased by an amount approximately equal to the volume of the chamber. The fixed opening of the chamber can limit the control of the fluid flow between the intake passage and chamber thereby limiting the potential improvements in engine performance produced by the chamber since the optimum amount of flow between the intake passage and chamber can vary depending on the operating conditions of the engine.